The invention provides a novel class of compounds, pharmaceutical compositions comprising such compounds and methods of using such compounds to treat or prevent diseases or disorders associated with abnormal or deregulated kinase activity, particularly diseases or disorders that involve abnormal activation of the Jak1, Jak2, Jak3, Tyk2, KDR, Flt-3, CDK2, CDK4, TANK, Trk, FAK, Abl, Bcr-Abl, cMet, b-RAF, FGFR3, c-kit, PDGF-R, Syk, PKC or Aurora kinases.
The protein kinases represent a large family of proteins that play a central role in the regulation of a wide variety of cellular processes and maintenance of cellular function. A partial, non-limiting, list of these kinases include: non-receptor tyrosine kinases such as the Janus kinase family (Jak1, Jak2, Jak3 and Tyk2); the fusion kinases, such as BCR-Abl, focal adhesion kinase (FAK), Fes, Lck and Syk; receptor tyrosine kinases such as platelet-derived growth factor receptor kinase (PDGF-R), the receptor kinase for stem cell factor, c-kit, the hepatocyte growth factor receptor, c-Met, and the fibroblast growth factor receptor, FGFR3; and serine/threonine kinases such as b-RAF, mitogen-activated protein kinases (e.g., MKK6) and SAPK2β. Aberrant kinase activity has been observed in many disease states including benign and malignant proliferative disorders as well as diseases resulting from inappropriate activation of the immune and nervous systems. The novel compounds of this invention inhibit the activity of one or more protein kinases and are, therefore, expected to be useful in the treatment of kinase-mediated diseases.
Spleen tyrosine kinase (Syk) (J. Bio. Chem., 1991, 266, 15790) is a non-receptor tyrosine kinase that plays a key role in immunoreceptor signaling in a host of inflammatory cells including B cells, mast cells, macrophages and neutrophils. Syk is related to zeta associated protein 70 (ZAP-70) but also demonstrates similarity with JAK, Src and Tec family kinases.
Syk plays a critical and specific role in B-cell receptor (BCR) signaling on auto-reactive B cells and in FcR signaling on mast cells, macrophages, osteoclasts and neutrophils. (See Immunology Today, 2002, 21(3), 148 and Current Opinion in Immunology 2002, 14(3), 341). Syk plays a key role in the activation mediated by Fc receptors of sentinel cells (mast cells and macrophages) and effector cells (neutrophils, basophils and eosinophils). The importance of Syk in rheumatoid arthritis is substantiated by data demonstrating the importance of Fc receptors (FcR) function and immune complexes in disease pathogenesis. Syk also mediates the activation of B cells through the BCR, which results in their expansion and the production of antispecific immunoglobulins. Therefore any disease that revolves around antibody-Fc receptor interactions may be modulated by Syk suppression. Thus a Syk inhibitor is likely to dampen both the initiation of the disease by blocking BCR signaling and the effector phase of the disease by blocking FcR signaling on macrophages, neutrophils and mast cells. Furthermore, blocking Syk would provide the added benefit of inhibiting osteoclast maturation and therefore attenuate bone erosions, joint destruction and generalized osteopenia associated with rheumatoid arthritis. Moreover, Syk acts upstream close to the receptors at the initiation of complex signaling events and thus its inhibition influences all responses elicited by the activating agent. In mast cells for example, inhibition of Syk blocks the early release of a number of granule contents, as well as the subsequent production and secretion of lipid mediators and cytokines. Syk inhibitors can thus impart multiple beneficial effects as each of these mediators play distinct roles in the integrated inflammatory response.
Inhibiting Syk should impact several critical nodes of the inflammatory cascade resulting in an effective and rapid suppression of the deleterious responses. Inhibiting Syk may be useful in treating a host of inflammatory and allergic diseases—for example (but not limited to), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), multiple sclerosis (MS) and type I hypersensitivity reactions such as allergic rhinitis, allergic conjunctivitis, atopic dermatitis, allergic asthma and systemic anaphylaxis. For a review on targeting Syk as a treatment of autoimmune and allergic disorders, see Expert Opin. Invest. Drugs, 2004, 13(7), 743.
Taken together, Syk inhibitors provide a broad modality to treat a host of inflammatory diseases and immunological disorders.